They look the same, But they're different
Sugar? Or salt?


Even though they look the same and are often confused, sugar and salt are very different. Like sugar and salt, not all black synthetic rubber is the same. This difference holds true when black synthetic rubber is used as a closed cell flexible elastomeric foam insulation.

Two commonly used synthetic rubber products, EPDM and NBR/PVC, are similar in appearance, but have very different performance properties that are not apparent just by looking at the two products. Aerocel insulation is made of EPDM - a synthetic rubber that offers superior weather and water resistance, making Aerocel Different and Better.

NBR/PVC products may not deliver on what is claimed. These are some of the greatest differences that could matter to a designer, installer or owner of a system that relies on performance.

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ASTM C 534, Grade 1

Standard Specification for Preformed Flexible Elastomeric Cellular Thermal Insulation in Sheet and Tubular Form

Minimum requirements

Thermal Conductivity - no greater than .30 @ 75°F mean temperature - tested by ASTM C 518 or ASTM C 177 or ASTM C 1114 or ASTM C 335
Water Vapor Transmission Rate - no greater than .10 perm-in. - tested by ASTM E 96, procedure A
Water Absorption - no greater than .2% by volume - tested by ASTM C 209
Linear Shrinkage - less than 7% - tested by ASTM C 534


Dimensional stability is a required property, and is NOT stated by an NBR/PVC producer. ASTM C 534 requires water absorption of no greater than 0.2% by volume. One product data sheet has dropped the decimal place, which is not acceptable since this decimal place is significant to indicate that the material performance is equal to or better than the established standard. This is a requirement for a product to meet ASTM C 534, Grade 1.

Hot surface performance is critical. One product states no cracking or delamination. These are only two of 10 observations required of ASTM C 411, the test of hot surface performance and upper service temperature, as detailed by ASTM C 534.

These materials may not meet the performance properties REQUIRED by ASTM C 534 for a Grade 1 product.

ASTM C 1534, Type 1

Standard Specification for Flexible Polymeric Foam Sheet Insulation Used as a Thermal and Sound Absorbing Liner for Duct Systems

Minimum requirements

Properties Required for Elastomeric Duct Liner:
Thermal Conductivity - .30 btu-in./hr.-ft.2-°F
Surface Burning Characteristics - Flame/Smoke 25/50 max.
Hot Surface Performance - 250°F, minimum
Water Vapor Sorption - 0.00%
Water Absorption - 0.2%
Dimensional Stability - 7% shrinkage max.
Odor Emission - Pass
Corrosiveness - Pass
Fungi Resistance - No Growth
Erosion Resistance - Pass
Sound Absorption Coefficients - 1/2" = .20NRC, 1"=.25NRC

Aeocel EPDM has been tested for ALL the above performance properties, and meets or exceeds ALL the requirements of flexible elastomeric closed cell foam duct liner. Aerocel is the ONLY flexible elastomeric foam duct liner product to meet ALL the requirements of this standard.

NBR/PVC products do NOT provide the service temperature required. These products may or may NOT provide the moisture resistance, dimensional stability, or corrosion testing required to meet the requirements of ASTM C 1534. The data is not presented.


Standard for the Installation of Air Conditioning and Ventilating Systems


Standard for the Installation of Warm Air Heating and Air Conditioning Systems

Both standards require material in duct, plenums, and other air handling space to have been tested by ASTM E 84 or UL 723, and be rated at flame spread of 25 or less and smoke developed of 50 or less. These standards require the service temperature MUST be 250°F MINIMUM, or greater, continuous use temperature.

Aerocel EPDM flexible elastomeric foam closed cell insulation delivers these properties in thicknesses from 1/8" thick to 2" thick.

Most NBR/PVC products do NOT deliver BOTH properties in the same product. One may have the fire safety characteristics, but not the service temperature, or vice-versa. The products in this comparison do NOT meet the temperature requirements in many thicknesses common to codes and standards.

UV Stable

Direct Exposure Tests, ASTM G7 & G90

Only EPDM rubber delivers real UV stability and resistance. This is the reason that rubber products that have to last in the weather, like roofing, is made from EPDM. Aerocel is tested for stability outdoors using direct exposure testing with no coatings, claddings, or jackets.

NBR/PVC products claim UV resistance, but only if not subject to extended periods of direct UV exposure. NBR/PVC insulation producers require covering these products with coatings or jacketing to avoid UV exposure.

NBR/PVC product data sheet claims*:

Painting or other protective jacketing is required for exterior applications.
For severe UV exposure (rooftop applications), reduction of surface defects, or for optimum performance, protective coating, or approved jacketing is required.

*This data sheet shows testing, but on closer inspection, the footnote requires coating or cladding.

Moisture Transport Properties

ASTM E 96 & C 209

EPDM rubber is used for moisture sealing and waterproofing because of its exceptional resistance to water and water vapor ingress. This resistance is enhanced by the nonpolar atomic structure of EPDM. The water vapor transmission properties are the best in the industry for flexible elastomeric rubber insulation, and the water absorption properties are the best, at .03% absorption by volume, per ASTM C 209.

NBR/PVC products have a high level of water absorption, and eventually will be dissolved by water in a few short years. In the meantime, NBR/PVC will act to transmit water through the matrix of the material with standard operation of building HVAC and refrigeration systems. ASTM C 534 requires water absorption of no greater than 0.2%. One product data sheet has dropped the decimal place, which is not acceptable. Is this to leave the impression of meeting or exceeding this performance requirement?

Inherent Microbial Resistance

EPDM is a naturally mold-and-mildew resistant material. No added biocides are required, delivering the same resistance year after year, long after the microbiocides have migrated out of NBR/PVC materials. This resistance results from tight cross-linking that creates a dense polymer, not allowing microbes to gain an attachment. EPDM contains no food source for microbial growth to sustain itself. EPDM's nonpolar nature won't allow water into the product. Aerocel passes all required microbiological growth testing WITHOUT the use of added micro biocides, delivering a healthy product for the duration of the structure.

NBR/PVC products provide both a food source and a water source for microbiological growth. Food in the form of plasticizers (PVC) and moisture from the higher affinity for water. Micro biocides are incorporated in these products to provide some of the resistance that EPDM naturally delivers. Even with the addition of microbiocides, these products can allow microbiological growth.

High and Low Service Temperature

ASTM C 411

EPDM rubber is routinely chosen as a flexible material that can provide long-term service at higher and lower temperatures than other synthetic rubber materials. This is demonstrated by Aerocel's higher service temperature for a single product. EPDM is used at temperatures as low as -320°F successfully. This is one of the properties that makes Aerocel an ideal choice for dual temperature applications, including dual-temp, two-pipe hydronic systems and VRF/VRV pipe systems.

NBR/PVC products are NOT designed for the extremes and are NOT selected when temperature extremes are required for service. The stated maximum of 220°F for these products is the best indicator of the limitations. When researched, the user may find this temperature is a short-term, spike temperature, not a continuous service temperature. Using a spike temperature causes improper product selection.

No Contribution to Corrosion Under Insulation (CUI)

ASTM 665 & 692

EPDM is the standard flexible elastomeric foam insulation that does not contribute to Corrosion Under Insulation or CUI.

Aerocel has been tested using ASTM C 692 for contribution to stress corrosion on austenitic stainless steel, and by ASTM C 665, the standard used for determining corrosion contribution for galvanized steel duct. Aerocel passes BOTH tests.

NBR/PVC products contain high enough levels of corrosion-causing fluoride, chloride, and bromide, which can accelerate corrosion when moisture is introduced. This ability to leach these corrosive compounds is a problem when moisture can be expected to impact the insulated system. To overcome this problem, NBR/PVC producers use special rubber blends that can provide the non-corrosive properties, at a far higher expense while sacrificing other properties that are required.

Aerocel® EPDM

Based on a closed cell design, Aerocel® EPDM is the most efficient and versatile elastomeric insulation on the market.

Aerocel® EPDM is designed for rugged applications including liquid cooling and heating pipes. And since EPDM synthetic rubber was designed many decades ago for use as an outdoor high-performance material, Aerocel® EPDM closed cell flexible insulation is inherently weather resistant – making it the perfect choice for harsh, outdoor applications.

Key Features

  • Works in high temperatures up to 257° F
  • Solar, radiant, low pressure steam, VRF/VRV Heating/Cooling
  • Works in low temperatures down to -297° F
  • Stays flexible in cold
  • Works with dual temperature systems
  • Use with chilled water or hot water systems
  • Works in high moisture / humid environments
  • Offering the most resistant rubber to moisture intrusion
  • No mold or mildew growth
  • Works in high moisture / humid environments
  • No sustenance in EPDM, biocides not required
  • Superior fire response properties
  • ASTM E 84 25/50 Flame and Smoke Rated, Exclusive ASTM C635 Self-Extinguishing

Get the only elastomeric insulation that works when and where others fail.